The invention relates to exploration of planets of the solar system other than Earth, particularly those planets whose atmosphere has a high density and a high temperature. The invention is of particular interest for exploration of the Venusian atmosphere which essentially consists of carbon dioxide whose temperaure and density variations with altitude have a profile which is particularly suitable for carrying out the process of the invention.
For that purpose, the process of the invention makes use of a buoyant assembly comprising an inflatable envelope which may be launched from Earth in folded condition and inflated with a vaporizable fluid when dropped in the Venusian atmosphere. Such assemblies consisting of an envelope and a container connectable with the envelope and containing a vaporizable liquid have already been suggested for inflation at high altitudes above sea level. Referring for instance to U.S. Pat. No. 3,107,068 to SIMKO et al, there is disclosed an inflatable closed envelope which is inflated by a liquid vaporizable at altitudes in excess of 150,000 feet upon opening of an enclosure which receives the envelope and container for launch. Similarly, U.S. Pat. No. 3,282,533 to SPAIN discloses a foldable expandable structure which may be inflated by vapor evolved from water or ice stored for launching and which vaporizes upon exposure to vacuum conditions which prevail at high altitudes. The purpose and function of such inflatable structures are entirely different from those of the present invention.
It has also been suggested to use a buoyant station balloon for exploring the Venus atmosphere (Journal of Spacecraft, Vol. 7, No. 7, July 1970, pp. 859-864). The balloon can carry a pay-load such as scientific apparatuses, radio-electric transmission apparatuses, radar reflectors, and the like. However, none of the proposed Venus stations is adapted for remaining at a self-stabilized predetermined altitude with vertical oscillations which remain within a limited range. Similarly, the inflatable enclosures which have been proposed for use in exploring the Earth atmosphere would not be adapted to such a stabilization, irrespective of the fact whether they are of the "open" type (which requires the use of a ballast and active means for controlling altitude and dropping amounts of ballast when required) or of the "closed" type.
It is an object of the invention to provide a process for exploring the high density high temperature atmosphere of a planet by means of a buoyant assembly which achieves automatic altitude stabilization without any requirement for active means. It is another object to provide such a buoyant assembly whose bulk and weight are suitable for launching from the Earth and which achieves altitude stabilization with a sufficient precision.
A process according to the invention comprises carrying a buoyant assembly from the Earth into the atmosphere of the planet to be explored. The assembly comprises an inflatable envelope which may be launched from the Earth in folded condition and a container connectable with said envelope and containing a vaporizable liquid. That liquid is selected to vaporize under the conditions prevailing in the atmosphere of said planet to an extent which decreases above said altitude and increases under said altitude for stabilization. The container may be separate from the envelope and connectable thereto by means which are actuated upon opening of an enclosure containing the envelope and container in the atmosphere of the planet. It may also consist of a thin wall container which is fractured by the vapor evolved from the liquid when subjected to the temperature and pressure which prevail in the atmosphere of the planet, particularly under the stabilization altitude.
The assembly may comprise one or more inflatable envelopes; in the latter case, the fluid in one envelope may be selected to provide an upwardly directed force at high altitudes, that is to have a positive buoyancy at all altitudes, while the other envelope receives a fluid selected to have a positive or negative buoyancy depending upon the altitude, for stabilization purpose.
Particular embodiments of the invention will now be described by way of examples, with particular reference to stations for exploration of the atmosphere of Venus.